As a vehicle decelerates to a stop whilst traversing terrain having a deformable, low-mu surface (e.g., sand, gravel, mud, or wet grass), the wheels of the vehicle may dig or sink into the soft surface of the terrain due, at least in part, to the brake torque and drag torque respectively applied to the wheels by the vehicle brake system and the surface of the terrain. The digging or sinking of at least certain of the vehicle wheels may be compounded or made worse in an instance wherein the vehicle is decelerating to a stop as it descends a slope having a deformable, low-mu surface. More particularly, as vehicle descends a slope, the weight of the vehicle is transferred to the “downhill” end of the vehicle (e.g., the front end when the vehicle is traveling in what is typically considered to be forward and the rear end when the vehicle is traveling in what is typically considered to be in reverse). This weight transfer, the effect of gravity, and the nature of the brake bias that favors the front axle/wheels of the vehicle, results in an increased vertical force being applied to the downhill end of the vehicle, which may cause one or more of the wheels at that end of the vehicle (i.e., the “leading” wheels) to dig or sink further into the surface than those at the “uphill” end (i.e., “trailing” wheels).
The digging or sinking of the vehicle wheel(s) may have a number of potentially adverse effects. For example, in an instance wherein the leading wheels of the vehicle are the steered or steerable wheels, the digging or sinking of one or more of those wheels may adversely affect the steering capability of the vehicle, and as such, it may prove difficult to follow a driver-intended line down the slope. Additionally, as the leading wheels dig or sink into the surface, a substantial amount of material forming the surface may build-up around them making it more difficult to subsequently pull away in a composed manner. This is because the vehicle must first overcome the build-up of material before progressing as desired (i.e., the vehicle wheels have to rise up through the material to a point where the tire(s) is/are on top of or at least relatively close to the surface before progressing).
Accordingly, it is an aim of the present invention to address, for example, the disadvantages identified above.